Is there a reason there are so few bitter mocktails with low sugar?

There are plenty of bitter cocktails with relatively low sugar (e.g. Negronis), but when i look for bitter mocktails they almost always have a ton of sugar.

I want a bitter, non-alcoholic, low-sugar drink with "bite" that I can have 5-6 of without feeling guilty, but I haven't found good recipes for this beyond soda water + bitters.

Is there some fundamental reason this combination of mocktail is impossible?